Least limiting water range in Spodosol and initial growth of sugarcane under soil bulk densities and salinities/ Intervalo Hidrico Otimo em Espodossolo e crescimento inicial da cana-de-acucar sob densidades aparentes e salinidade do solo

The impacts of agricultural mechanization and soil management on sugarcane activity may compromise the growth of plants. This study aimed to evaluate the initial growth of sugarcane (Saccharum officinarum) at soil densities under two salinity conditions, associated with the least limiting water range (LLWR), and obtain the critical density for the Spodosol. The treatments consisted of the use of five bulk densities (1.40; 1.50; 1.60; 1.70 and 1.80 Mg [m.sup.-3]) and two conditions of soil salinity (ECse = 0.5 and 3.0 dS [m.sup.-1]). Morphological variables and biomass of sugarcane plants were measured and, simultaneously, undisturbed soil samples were collected in the layers of 0.02-0.08 m to determine the water retention curve, soil resistance to penetration and the least limiting water range. In general, it was concluded that sugarcane plants has higher growth between the bulk densities of 1.50 and 1.60 Mg [m.sup.-3]. The salinized soil showed higher LLWR than the non-salinized soil, leading to higher shoot fresh mass at bulk densities between 1.49 and 1.66 Mg [m.sup.-3]. The critical bulk densities observed for the Spodosol were 1.70 Mg [m.sup.-3] for the non-salinized soil and 1.77 Mg [m.sup.-3] for the salinized soil. Key words: Saccharum officinarum, soil compaction, soil resistance to root penetration, soil physical quality Os impactos da mecanizacao agricola e o manejo do solo na atividade canavieira podem comprometer o crescimento das plantas. O objetivo deste estudo foi avaliar o crescimento inicial da cana-de-acucar (Saccharum spp.) sob densidades do solo em duas condicoes de salinidade, associado ao intervalo hidrico otimo (IHO) e obter a densidade critica para o Espodossolo. Os tratamentos consistiram da utilizacao de cinco densidades de solo (1,40; 1,50; 1,60; 1,70 e 1,80 Mg [m.sup.-3]) e duas condicoes de salinidade do solo (CEes = 0,5 e 3,0 dS [m.sup.-1]). Realizaram-se medicoes de variaveis morfologicas e massa vegetal das plantas de cana-de-acucar e paralelamente coletaram-se amostras indeformadas de solo nas camadas de 0,02-0,08 m, para determinacao da curva de retencao de agua, da resistencia do solo a penetracao e o intervalo hidrico menos limitante. Concluiu-se de forma geral que houve maior crescimento das plantas entre as densidades de solo de 1,50 e 1,60 Mg [m.sup.-3]. O solo salinizado apresentou maior IHO que o solo nao salinizado, refletindo em maior massa fresca da parte aerea para valores de densidades do solo entre 1,49 e 1,6